The invention concerns an overrunning clutch for receiving a shaft, said overrunning clutch comprising an outer ring having clamping surfaces, a cage for guiding clamping rollers and comprising spring elements for suspending the clamping rollers being arranged in the outer ring.
An overrunning clutch of the pre-cited type configured as a sleeve-type overrunning clutch is known from DE 42 10 560 C2. This overrunning clutch comprises a chiplessly shaped sleeve having a rim. An inner peripheral surface of the sleeve comprises clamping ramps against which spring-loaded clamping needle rollers guided in a cage bear in the clamped state. To avoid so-called edge abrasion, i.e. a life-reducing overloading of end regions of the clamping rollers, the two opposite end faces of the clamping needle rollers are slightly rounded.
A drawback of this is that, despite this diameter reduction in the end regions of the clamping rollers, assembly problems can arise during automatic assembly. Particularly in the case of a very sharp-edged shaft, the end face of the shaft can collide against the end faces of the clamping rollers when being pushed in axially. Even when rotated in overrunning direction, not all the clamping rollers are turned out of the clamping gaps, so that a trouble-free automatic assembly is not possible. This is due to the fact that in the unassembled state, the springs for the clamping needle rollers press them against the next crossbar or against the next needle retaining element with the result that the clamping contour presses the clamping needles or rollers radially inwards. As a result, the enveloping circle diameter of the unassembled overrunning clutch is smaller than the diameter of the shaft. When the shaft is pushed in axially, a collision takes place between the shaft and the clamping rollers and this can lead to a destruction of the cage or of the entire overrunning clutch arrangement.
In this connection, other clamping rollers likewise having a diameter reduction in their end regions are also known. Thus, for example, DE-OS 16 25 743 describes a clamping roller overrunning clutch in which trumpet-like pegs are arranged on the opposite ends of the clamping rollers. However, these pegs have nothing at all to do with the assembly of the overrunning clutch arrangement but only prevent the clamping rollers from falling out inwards in radial direction. Even DE-OS 25 14 767 and DE 24 38 007 C2 disclose overrunning clutches whose clamping rollers have a reduced diameter in their end regions. Here, too, the purpose is only the retention of the rollers.
It is therefore an object of the invention to provide a clamping roller overrunning clutch that enables an automatic assembly with the associated shaft without difficulty.
This and other objects and advantages of the invention will become more obvious from the following detailed description.
The invention achieves the above objects by the fact that the clamping rollers comprise a bevel on at least one end face so that in an uninstalled state of the shaft, the enveloping circle diameter DHK at an outer end of the frustum is equal to or larger than the diameter DW of the shaft. Through this inventive radial matching of the clamping roller and the shaft, it is guaranteed that the shaft can be pushed in between the clamping rollers without obstruction and, in doing so, presses the clamping rollers radially outward against the inner peripheral surface of the outer ring of the overrunning clutch.
According to a further proposition of the invention, the bevel may be configured with a frustoconical, convex, concave or any other desired shape. In this connection, it is also conceivable to configure the bevel with a combination of straight and curved lines.
Finally, according to another advantageous feature of the invention, the bevel is inclined at an angle of 60 to 75xc2x0 to the end face of the clamping roller. This assures that as little as possible of the axial clamping surface is lost.
The invention will now be elucidated with reference to one example of embodiment described below.